Rapidly advancing health technology has the potential to dramatically improve the health of older Americans. However, technological progress is accompanied by rising costs, making access to health insurance crucial for both the economic security and quality of life of the elderly. Although the Medicare program provides nearly universal coverage for a basic set of benefits for those aged 65 and older, the coverage has important gaps. As a result, most beneficiaries are able and choose to supplement Medicare through a variety of private and public programs. However, considerable variation exists among beneficiaries in the choices available to them and the coverage they obtain. The objective of this research is to examine the factors influencing elderly Medicare beneficiaries' supplemental coverage choices. The project has two specific aims: 1) to construct a study dataset that provides detailed information over time on both health, socioeconomic, and demographic characteristics of Medicare beneficiaries and the types and characteristics of supplemental coverage available to them; and 2) to determine how individual demographic, health, and socioeconomic status, market trends, and Medicare policies affect access to supplemental coverage among Medicare beneficiaries. I will achieve the first objective by linking data from the Health and Retirement Survey (HRS) with external data sources describing the availability and features of supplemental coverage for Medicare beneficiaries based on both their individual characteristics and their geographic location. I will achieve the second objective by using the study dataset to estimate multivariate models of insurance choices among Medicare beneficiaries. These models will take advantage of the longitudinal survey data and detailed and innovative survey questions available in the HRS to examine a variety of factors affecting Medicare beneficiary supplemental coverage choices. If I achieve these objectives, I will have created a powerful and unique dataset that can be used to examine many issues related to the insurance coverage of the elderly, particularly as survey years are added to the HRS. The project will allow me to assess the value of particular experimental question in the HRS for models of health insurance choices. In addition, I will have provided new evidence regarding the influence of individual characteristics such as health status and health expectations, cognitive ability, demographic characteristics and socioeconomic status and the effects of public policies on coverage choices.